1. Field of the Invention
The invention generally relates to underwater pipelines, and more particularly, to stabilizing elevated pipelines after installation using grout bags for forming pedestals.
2. Description of the Related Art
Subsea pipelines or structures supported on the seabed often require the underwater construction of pedestals or sleepers where the pipeline would otherwise be unsupported for a given length. Construction of these supports requires both accurate placement of the support under the pipeline or structure, and the flexibility to adapt the support to various seabed conditions. In many cases the use of divers in the construction process is infeasible and operations must be conducted entirely by remote means. Under these circumstances a highly reliable and accurate means of support placement is particularly important.
One support construction technique involves the placement of collapsed bags beneath the pipeline or structure. The bags are then filled with grout until they rest on the seabed and support the pipeline or structure. Existing methods of grout bag placement require manual placement by visual means or attachment of the placement apparatus to the pipeline or structure.
Bag placement is generally slow and imprecise if done using remotely operated vehicles (ROV's). Attachment of the placement apparatus to the pipeline or structure imposes undesirable loads on the pipe or structure, may damage the pipe or structure, and makes accurate bag placement difficult for sloping pipelines or structures. In addition, existing bag placement methods and apparatus do not adequately compensate for a sloping seabed.
Therefore, there is a need for an apparatus which can be easily located remotely, does not attach to the pipeline, and can be used on sloping seabeds.